JP2009526367A - System and method of shutdown for fuel cell system operation and corrosion prevention - Google Patents

Abstract

A fuel cell stack is provided that includes a plurality of fuel cells, each including a membrane electrode assembly that is inserted between an anode and cathode flow field plate forming an anode and a cathode channel, respectively. A storage device is positioned downstream of the fuel cell stack. The purge control device is positioned downstream of the storage device operable in a first state allowing fluid communication between the anode and cathode channels and in a second state separating the oxidant outlet from the storage device. Some embodiments include a purge control device between the anode channel and the storage device. A method of operating a fuel cell stack includes selectively purging fluid from the fuel cell stack into the storage device first and selectively purging fluid from the storage device a second time after the first. Steps.

Description

(Citation of related application)
This application is US Provisional Patent Application No. 60 / ______ filed on Feb. 7, 2006 (formerly US Patent Application No. 11/350263, which was changed to a provisional application on request of January 17, 2007) ) And claims the benefit of Section 119 (e) of U.S. Patent Law, which is hereby incorporated by reference in its entirety.

(Field of Invention)
The present invention relates to electrochemical energy converters having ion exchange membranes, such as fuel cells or electrolyzer cells or stacks of such cells, and more particularly to systems for using them to prevent corrosion and Regarding the method.

(Description of related technology)
An electrochemical fuel cell comprising an ion exchange membrane, such as a proton exchange membrane (PEM), is typically used as a fuel cell in which fuel and oxidant are electrochemically converted at the fuel cell electrode to produce power, or external current It can be operated as an electrolytic cell that passes between the fuel cell electrodes through water and provides hydrogen and oxygen production at each electrode. 1-4 collectively illustrate an exemplary design of a conventional membrane electrode assembly 5, an electrochemical fuel cell 10 with PEM 2, a stack 100 of such fuel cells, and a fuel cell system 400.

  Each fuel cell 10 includes a membrane electrode assembly (“MEA”) 5 such as that illustrated in the exploded view of FIG. The MEA 5 comprises a PEM 2 inserted between the first and second electrode layers 1, 3 that are typically porous and conductive, each of which is in contact with the PEM 2 to drive the desired electrochemical reaction. An electrocatalyst is provided at the interface. The electrocatalyst generally defines the electrochemically active area of the fuel cell. The MEA 5 is typically reinforced as a bonded laminated assembly.

  In the single fuel cell 10 illustrated in the exploded view of FIG. 2, the MEA 5 is inserted between first and second separator plates 11, 12 that are typically fluid impervious and conductive. Separators 11, 12 are manufactured from non-metals such as graphite, metals such as certain grades of steel or surface-treated metals, or conductive plastic composite materials.

  A fluid flow space, such as a passage or chamber, is provided between the separator plates 11, 12 and the adjacent electrode layers 1, 3 to facilitate reactant access to the electrode layers and product removal. Such a space is formed by using, for example, a spacer between the separation plates 11 and 12 and the corresponding electrode layers 1 and 3, or a mesh between the separation plates 11 and 12 and the corresponding electrode layers 1 and 3. It can be provided by providing a porous fluid fluidized bed. More generally, the channel or flow field is formed on the surface of the separator plates 11, 12 facing the electrode layers 1, 3. Separating plates 11, 12 comprising such channels are generally referred to as fluid flow field plates. In a conventional fuel cell 10, a resilient gasket or seal is typically provided around the flow field between the face of the MEA 5 and each of the separator plates 11, 12 to leak liquid reactant and product streams. prevent.

  An electrochemical fuel cell 10 having an ion exchange membrane, such as PEM2, sometimes called a PEM fuel cell, is advantageously stacked and comprises a plurality of fuel cells disposed between first and second end plates 17,18. A stack 100 (see FIG. 3) is formed. A compression mechanism is typically employed to hold the fuel cell 10 together, to maintain good electrical contact between the parts, and to compress the seal. As shown in FIG. 2, each fuel cell 10 includes a pair of separation plates 11 and 12 in a configuration with two separation plates for each MEA 5. A cooling space or layer can be provided between some or all of a pair of adjacent separator plates 11, 12 in the stack 100. In an alternative configuration (not shown), a single separator plate, or “bipolar plate”, is inserted between a pair of MEAs 5 in contact with the cathode of one fuel cell and the anode of an adjacent fuel cell, Therefore, there is only one separator for each MEA 5 in the stack 100 (excluding the terminal battery). Such a stack 100 can comprise a cooling bath that is inserted between several fuel cells 10 in the stack, rather than between each adjacent pair of fuel cells.

  The illustrated fuel cell element has an opening 30 formed therein and aligned in a stacked assembly to provide a cooling space for the supply and discharge of reactants and products, respectively. If it is, form a fluid manifold for the refrigerant. Again, a resilient gasket or seal is typically provided between the face of the MEA 5 and each of the separator plates 11, 12 around these fluid manifold openings 30, and the fluid in the working stack 100. Prevents flow leakage and mixing.

  Commercial implementation of an electrochemical system or instrument including electrochemical fuel cell 5 and / or stack 100 may be hampered by corrosion of the stack during startup and / or shutdown in some cases. FIG. 4 illustrates a fuel cell system 400 that includes the fuel cell stack 100. At startup, air may be present in the anode channel 402 of the stack 100. Corrosion can occur while hydrogen is supplied to the stack inlet at start-up, with air downstream of the anode channel 402 and hydrogen upstream. The duration of this corrosion event can be minimized or reduced by passing the hydrogen front through the stack 100 at a higher speed. Thus, several methods have been developed to reduce corrosion in the stack.

  One way to mitigate start-up corrosion, which is generally applicable to automotive systems, is to use an anode recycling blower to avoid excess fuel and / or nitrogen that diffuses from the cathode outlet to the anode chamber from the anode outlet. Facilitates removal of active fluid and returns them to the inlet. In another method, a large purge valve allows excess fuel and / or inert fluid in the anode chamber to be removed. However, these methods have obstacles. For example, anode recycling fans are expensive and generally unreliable, making their use expensive and the results unpredictable. Large purge valves are bulky and equally expensive, creating additional problems for use in confined spaces such as automobiles. In addition, large purge valves can vent fuel and inert fluids such as nitrogen.

  Additional opportunities for corrosion to occur in the stack 100 exist during the stack 100 outage. After shutdown, fuel, such as hydrogen, flows out of the anode chamber of each fuel cell by diffusion across the membrane 406 and is consumed in the cathode chamber of the same fuel cell. The anode pressure then drops and air can be absorbed through openings or channels in the MEA 5 or through leaks. This air can corrode elements of the fuel cell 10 and / or assembly parts of the stack 100 during startup of the stack 100. Previously proposed solutions for mitigating corrosion during or after shutdown include introducing additional hydrogen into the anode channel 402 or attempting to avoid leakage of air into the stack 100. . However, the use of excess fuel, such as hydrogen, that is not used for the operation of the electrochemical system or instrument results in a costly waste of fuel. Also, despite efforts to prevent leakage, it is not possible to completely avoid any leakage in any application.

  Commercial commercialization of fuel cells is also increasingly dependent on fuel efficiency and hydrogen emissions. Existing solutions include a single solenoid purge valve that typically presents unclear flow control and water drop and particle contamination problems. Multiple purge valve arrangements, on the contrary, are more expensive and have a complex arrangement. Other solutions include control valves that operate similarly to fuel injectors, but such valves require additional power and are generally complex to control. Metering devices are also used, but such devices tend to experience leaks and are generally expensive. Still other solutions include larger valve openings with flow restrictors having small openings that are susceptible to water droplets or particulate contamination.

  A cost-effective, compact, and reliable system and / or method prevents corrosion formation during start-up, shutdown, and load transients in electrochemical fuel cells and fuel cell stacks, and fluids from the fuel cell stack It is necessary to provide improved control of the purge.

  According to one embodiment, the electrochemical system comprises a plurality of fuel cells forming a fuel cell stack, each fuel cell having a membrane with an ion exchange membrane inserted between the anode electrode layer and the cathode electrode layer. An electrode assembly (MEA) and an anode flow field plate adjacent to the first side of the MEA, the anode flow field plate configured to direct hydrogen-containing fuel to at least a portion of the first side of the MEA; A cathode flow field plate adjacent to the second side of the MEA, the cathode flow field plate configured to direct oxidant to at least a portion of the second side of the MEA; and downstream of the fuel cell stack At least one storage device positioned and in fluid communication therewith, the storage device operating to store and dispense fluid, and an oxidant outlet positioned downstream of the fuel cell stack And a first purge control device positioned downstream of the storage device, wherein the first state enables fluid communication between at least a portion of the anode flow field plate and at least a portion of the cathode flow field plate And a first purge control device operable in a second state separating the oxidant outlet from the storage device.

  According to one aspect of the above embodiment, the electrochemical system includes a recirculation line that is in fluid communication with at least a portion of the fuel cell stack and that operates to recirculate at least one fluid.

  According to another embodiment, each fuel cell is a membrane electrode assembly (MEA) having an ion exchange membrane inserted between the anode and cathode electrode layers and an anode flow field plate positioned adjacent to the anode electrode layer. An anode flow field plate configured to direct hydrogen-containing fuel from a fuel source to at least a portion of the anode electrode layer, and a cathode flow field plate positioned adjacent to the cathode electrode layer, wherein the oxidant supply A cathode flow field plate configured to direct oxidant from a source to at least a portion of the cathode electrode layer; and at least one storage device in fluid communication with at least a portion of at least one of the anode and the cathode electrode layer. A method for discontinuing operation of an electrochemical system having a plurality of fuel cells forming a fuel cell stack comprises: Disconnecting the main load from the fuel cell, ending the supply of fuel to the disconnected fuel cell stack, and, after ending the supply of fuel, substantially removing oxygen from the air in the disconnected fuel cell stack. Consuming and forming oxygen-deficient air therein, and providing at least one of hydrogen and nitrogen to at least a portion of at least one of the anode electrode layers from the storage device .

  According to yet another embodiment, each fuel cell is positioned adjacent to the anode electrode layer, with a membrane electrode assembly (MEA) having an ion exchange membrane inserted between the anode and cathode electrode layers, to the anode electrode layer. An anode flow field plate configured to induce hydrogen-containing fuel; a cathode flow field plate positioned adjacent to the cathode electrode layer and configured to direct oxidant to the cathode electrode layer; and downstream of the fuel cell stack At least one storage device positioned in the fuel cell stack; a cathode inlet positioned upstream of the fuel cell stack; an oxidant outlet positioned downstream of the fuel cell stack; and an anode flow field plate and the cathode positioned downstream of the storage device A first state allowing fluid communication with the flow boundary plate, and a second state separating the oxidant outlet from the accumulator A first purge control device operable at a first state, a first state positioned between the fuel cell stack and the storage device and enabling fluid communication between the anode flow field plate and the storage device, and an anode flow An operation of an electrochemical system having a plurality of fuel cells forming a fuel cell stack comprising a second purge control device operable in a second state to discontinue fluid communication between the interface plate and the storage device. The method first operates upon the first state upon detecting a fuel cell stack purge state, and the second purge control device operates to purge fluid from the anode flow field plate to the storage device. The second purge control device for operating in the second state, and the second time after the first time, the first purge control device is opened and the storage device is Caso Purging at least to one fluid of de entrance detects the storage device purge state, and performing a storage device purge.

  According to yet another embodiment, each fuel cell is positioned adjacent to the anode electrode layer with a membrane electrode assembly (MEA) having an ion exchange membrane inserted between the anode and cathode electrode layers and into the anode electrode layer. An anode flow field plate configured to induce hydrogen-containing fuel; a cathode flow field plate positioned adjacent to the cathode electrode layer and configured to direct oxidant to the cathode electrode layer; and downstream of the fuel cell stack At least one storage device positioned in the fuel cell stack, a first state positioned between the fuel cell stack and the storage device and allowing fluid communication between the anode flow field plate and the storage device, and an anode flow field plate A plurality of fuels forming a fuel cell stack comprising a purge control device operable in a second state to cease fluid communication between the fuel cell and the storage device A method of operating an electrochemical system having a pond comprises detecting an increase in load applied to the fuel cell stack and a decrease in at least one of the pressure and concentration of oxidant in the fuel cell stack; Operating in the second state, increasing at least one of the pressure and concentration of the hydrogen-containing fuel in the fuel cell stack, and closing the purge controller to balance the pressure difference in the fuel cell stack Including.

  According to a further embodiment, each fuel cell is positioned adjacent to the anode electrode layer with a membrane electrode assembly (MEA) having an ion exchange membrane inserted between the anode and cathode electrode layers, and contains hydrogen to the anode electrode layer. An anode flow field plate configured to direct fuel, a cathode flow field plate positioned adjacent to the cathode electrode layer and configured to direct oxidant to the cathode electrode layer, and positioned downstream of the fuel cell stack A first state positioned between the fuel cell stack and the storage device and allowing fluid communication between the anode flow field plate and the storage device, and the anode flow field plate and storage A plurality of fuel cells comprising a purge control device operable in a second state to cease fluid communication with the device and forming a fuel cell stack; The method of operating the electrochemical system comprises detecting a decrease in load applied to the fuel cell stack and a decrease in at least one magnitude of the pressure and concentration of the oxidant in the fuel cell stack; Operating at 1 state, reducing at least one of the pressure and concentration of the hydrogen-containing fuel in the fuel cell stack, and opening the purge controller to balance the pressure difference in the fuel cell stack; Including.

  An “embodiment” or “embodiment” referred to throughout this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. means. Thus, the phrases “in one embodiment” or “in an embodiment” used in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

  In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the art will recognize that embodiments may be practiced without one or more of these specific details, or by other methods, components, materials, and the like. Let's go. In other cases, well-known structures associated with accumulators and diaphragms and associated with electrochemical cell systems such as but not limited to flow boundary plates, end plates, electrocatalysts, external circuits, and / or recirculation devices What has not been shown or described in detail to avoid an unnecessarily vague description of the embodiments.

  References throughout this specification to “electrochemical system”, “fuel cell”, “fuel cell stack”, “stack”, and / or “electrolyzer” are not intended to be limiting and include fuel and oxidation. Any device, instrument, in which the agent is electrochemically converted to produce power, or external current passes between the fuel cell electrodes, typically through water, resulting in the production of hydrogen and oxygen at each electrode, Or to point to the system.

  “Fuel” and / or “hydrogen”, as referred to throughout this specification, are not intended to be limiting, but can be separated into protons or electrons in a given chemical reaction to assist in the electrochemical conversion. It is intended to refer to any reactant or gas that produces electrical power.

  “Oxidizing agent”, “air”, and / or “oxygen” as referred to throughout this specification is not intended to be limiting, but is not limited to oxygen, water, water vapor, air, or the like. It is intended to refer to any liquid or gas capable of oxidizing things.

  “Ion exchange membrane”, “proton exchange membrane”, and / or “PEM”, as referred to throughout this specification, are not intended to be limiting, but ions of a first charge or polarity are in a first direction. Any membrane, structure, or material that blocks passages in the first direction of ions of the second charge or polarity opposite the first charge or polarity while allowing passage through the membrane Is intended to point to.

  “Accumulator”, “accumulator”, “accumulator”, and / or “accumulator” as referred to throughout this specification are not intended in a limiting sense, but receive and dispense gas, Alternatively, it is intended to refer to any device, instrument, container, at least partially bounded volume, or structure that operates to store or store a dose of compressed gas.

  References throughout this specification to “flow control device”, “purge valve”, “purge control device”, and / or “valve” are not intended to be limiting, but any instrument, valve, instrument Can be used to manage fluid movement from a location such as a computer controller, or pump, or a fuel supply to a first volume, or a second volume, or a location such as an electrode layer It is intended to refer to any device.

  In one embodiment as illustrated in FIG. 5, a fuel cell stack incorporating a plurality of fuel cells, each fuel cell having an anode channel 502, a cathode channel 504, and an ion exchange membrane 506 such as a PEM inserted therebetween. An electrochemical system 500 including 501 is provided. The first flow controller 508 controls the supply flow rate of fuel such as hydrogen from the fuel supply source 510 to the anode channel 502. The second flow controller 512 controls the supply flow rate of an oxidant such as oxygen or air from the air supply source 514 to the cathode channel 504. Typically, during operation, the anode (or fuel) pressure is greater than the cathode (or oxidant) pressure.

  When fuel is introduced from the fuel supply 510 into the system 500, the first electrocatalytic layer at least partially in contact with the anode divides the hydrogen molecules into protons and electrons, and the protons pass through the membrane 506 in a first direction. On the other hand, electrons are sent to an external circuit to generate electric power. Protons travel through the membrane 506 and through the cathode channel 504 and combine with the electrons returning from the external circuit and oxygen supplied from the air source 514 to the cathode and from the system 500 as exhaust gas or liquid, or both. Produce water, heat, and / or other by-products to be purged.

  Referring to FIG. 4, air may be present in the anode channel 402 when the existing fuel cell system 400 is started. When hydrogen is introduced into the anode channel 402, corrosion may occur if air remains in the downstream portion of the fuel cell.

  In one embodiment of the invention shown in FIG. 5, the fuel cell system 500 includes a storage device 516 having a volume 518 and positioned downstream of the stack 501. The accumulator 516 is in fluid communication with at least one of the anode and cathode channels 502, 504, and is an accumulator as shown in the illustrated embodiment of FIG. 5, or at least such as hydrogen, oxygen, and nitrogen. It may be any device capable of receiving, storing, and dispensing a fluid and / or storing and / or compressing the same.

  When the first flow control device 508 is in the open position, the hydrogen-containing fuel flows from the fuel supply source 510 to the stack 501. Any air present in the stack 501, particularly the anode channel 502, is pushed out by the inflow of hydrogen-containing fuel, and at least a portion of the air flows into the storage device 516.

  The system 500 purges with a solenoid, or rotating disk, sphere, or plug, or any other suitable flow control device for releasing reactants, products, and / or byproducts from the fuel cell stack 501. A first flow controller 520, such as a valve, may further be included. For example, if the system 500 stops operating, air may penetrate into the anode channel 502, and fuel may be introduced into the anode channel 502 and corrosion may occur as the air is purged therefrom. To prevent corrosion, some existing fuel cell systems, such as the system 400 illustrated in FIG. 4, may have a large purge so that the air in the anode channel 402 can be quickly expelled when fuel is introduced. It has a valve 420. Since the purge rate of air from the anode channel of the fuel cell stack of the system 400 is the same as the exhaust rate of air through the purge valve 420, purge valves such as the large purge valve 420 of the system 400 are typically large. Including openings. However, large purge valves can indicate the feasibility of a fuel cell system for various applications, such as ventilation applications, for example in automobiles. In addition, large purge valves discharge large amounts of waste products, including air and fuel, which can be wasteful and result in high hydrogen emissions.

  In contrast, in the illustrated embodiment of FIG. 5, the first purge controller 520 need not have a large opening for purging fluid, such as air, from the anode channel 502 in a rapid manner upon startup. . This is because the pushed out air flows into the volume 518 of the storage device 516.

  Accordingly, the storage device 516 provides effective exhaust of air and / or other reactants, products, and inert gases such as nitrogen from the stack 501 while air, reactants to the surrounding environment. , And / or prevent mass discharge of products. Reducing the discharge rate and volume of waste products from the system 500 minimizes or reduces the size of the first purge controller 520 and implements the use of the system 500 in applications where space is limited. Increase the possibility.

  Accumulator 516 can be sized to maintain a desired amount of fluid being drained from first purge controller 520. The optimal level of fluid being drained from the first purge controller 520 can be determined based on a given application and / or its size requirements. In the illustrated embodiment of FIG. 5, a purge line 521 extending from the first purge controller 520 is connected to a flow 517 from the outlet of the cathode channel 504, but in addition or alternatively, a vent. 540 may be connected.

  Further, in some embodiments, the cross-sectional area of the storage device 516 may be greater than the cross-sectional area of a line, pipe, or any other component that communicates flow to and / or from the storage device 516. Good. In some embodiments, the volume 518 of the storage device 516 may be substantially the same as the total volume of the anode channel 502 of the fuel cell stack 501.

  An additional opportunity for corrosion to occur is during shutdown of the existing system 400 shown in FIG. After shutdown, the first flow controller 408, which controls the fuel flow rate, is closed to minimize fuel consumption, and fuel such as hydrogen is diffused from the membrane 406 to the cathode and with residual oxygen therein. Is lost from the anode. The pressure in the anode channel 402 then drops rapidly, causing the anode to absorb air from the cathode through openings or channels in the membrane 406 or through a leak outlet. This air can cause corrosion of elements of the fuel cell system 400 and / or assembly components of the fuel cell stack 100.

  However, in the system 500 of embodiments of the present invention, when the first flow controller 508 is closed, hydrogen diffusion from the anode channel 502 through the membrane 506 to the cathode channel 504 and residual oxygen in the cathode channel 504 are reduced. Due to the reaction, the pressure in the anode channel 502 decreases. Furthermore, the anode absorbs some of the fluid from the storage device 516 downstream of the stack 501 containing hydrogen containing fuel and an inert gas such as nitrogen until oxygen in the cathode is substantially consumed. As hydrogen is withdrawn from the storage device 516 to the anode channel 502, air can be withdrawn from the vent 540 and / or a gas, such as oxygen-deficient air, is withdrawn from the cathode to replace the withdrawn hydrogen. be able to. At the same time, the first purge controller 520 can be opened so that the anode and cathode channels 502, 504 are at the same pressure while the concentration of oxygen in the cathode is reduced, thus from the cathode channel 504 to the anode channel 502. Air is prevented from crossing the membrane 506.

  FIG. 6 shows that the injection pump 622 is used to recirculate the anode gas through the recirculation line 623 and prevent gas or liquid such as nitrogen or water, respectively, from blocking the anode channel 602. Figure 8 illustrates an electrochemical system 600 according to another embodiment of the invention. Electrochemical system 600 further includes first and second flow controllers 608, 612 for controlling the flow rates of fuel and oxidant from fuel source 610 and oxygen source 614, respectively. The electrochemical system 600 may further include a first purge controller 620. In the illustrated embodiment of FIG. 6, the purge line 621 extending from the first purge controller 620 is connected to the flow 617 from the outlet of the cathode channel 604, but in addition or alternatively, the vent. 640 may be connected.

  In addition, those skilled in the art will appreciate that the additional volume in the anode loop resulting from the accumulator 616 can cause a pressure swing (eg, operational tension) across the anode channel 602 by absorbing and discharging fluid within the anode. It will be appreciated that when operating in mode, it can be mitigated (due to periodic purge of the anode).

  In yet another embodiment, as illustrated in FIG. 7A, the electrochemical system 700 includes a storage device 716 having 718 with a diaphragm 724 therein. The diaphragm 724 can be utilized to maintain a desired cross pressure of the stack 701 (eg, a pressure differential between the anode and cathode) during normal operation, load transients, start-up, and / or shutdown. Maintaining the desired transverse pressure of the stack 701 may result in unwanted pressure swings and / or the introduction of air into the system 700 that may cause hydrogen permeation through the membrane 706 or corrosion as described herein. Prevent possible vacuum. In addition or alternatively, the position of the diaphragm 724 can be an indicator of the transverse pressure so that the feed fuel flow rate can be controlled. This information can be returned to the source 710 to increase or decrease the fuel flow rate, thus adjusting the transverse pressure by controlling the fuel flow rate.

  Electrochemical system 700 further includes first and second flow controllers 708, 712 for controlling the flow rates of fuel and air from fuel source 710 and air source 714, respectively. The electrochemical system 700 may further include a first purge controller 720. In the illustrated embodiment of FIG. 7A, the purge line 721 extending from the first purge controller 720 is connected to the flow 717 from the outlet of the cathode channel 704, but in addition or alternatively, the cathode inlet. (Eg, upstream of the cathode channel) or vent 740 may be connected.

  As illustrated in FIG. 7B, in some embodiments, the storage device 716 and / or the diaphragm 724 may be or comprise a bias pressure device 727. The bias pressure device 727 may include any biasing member such as a spring or actuator 729 that can withstand the piston 731 on the anode side and minimize the anode volume. The piston 731 can be provided with a seal 733 around it to prevent leakage. Without being limited by theory, in the case of a downward transient (that is, a decrease in load), the cathode pressure decreases as shown in FIG. 7C, and the piston 731 can be advanced toward the cathode. This increases the volume 735 of the storage device 716 that is configured to be in fluid communication with the anode channel 702. Thus, the pressure in the anode channel 702 is reduced, reducing the cross pressure between the anode and cathode layers. When the hydrogen is consumed and / or purged and the downward transition is complete, the piston 731 at least substantially occupies its original position illustrated in FIG. 7B.

  In yet another embodiment, as shown in FIG. 8, the electrochemical system 800 can attach a plug flow device 826 instead of or in addition to the storage device 816. The plug flow device 826 can be in fluid communication with the flow of gas exhausted from the cathode channel 804 such that the cross pressure of the stack 801 is passively adjusted. The plug flow device 826 is typically narrow in cross section with a high length to diameter ratio and typically contains purge gas at one end and air or cathode gas or both at the other end. The forefront between two such gases can be adjusted during start-up, shutdown, and / or load transients to adjust the cross-over pressure of the stack 801.

  In addition, a volume in which the gas can mix, such as the volume 818 of the storage device 816, is located downstream of the plug flow device 826 to prevent unintentional release of fuel into the cathode channel 804 or into the vent 840. it can.

  Additionally or alternatively, sensors 828, 830, such as oxygen or hydrogen sensors, or both, are coupled to the plug flow device 826, or a storage device according to any of the previous or subsequent embodiments. Located in at least one line, the fluid component of the gas (eg, oxygen and hydrogen concentrations) can be detected. These sensors 828, 830 can be selectively placed at different points in the line leading to or extending from the plug flow device 826, the supply flow rate of fuel such as hydrogen to the anode channel 802, And / or can be electrically coupled to flow controllers 808, 812 that control the flow rate of an oxidant, such as air, to the cathode channel 804. Sensors 828, 830 can communicate fluid component information to flow controllers 808, 812 to control the supply fuel flow rate or supply air flow rate, or both, to the anode channel 802 or cathode channel 804, respectively. In addition or alternatively, information from sensors 828, 830 can be used to control first purge controller 820, for example, first purge controller 820 after the shutdown is complete. close.

  The inventors contemplate embodiments of the present invention that may or may not incorporate all the described components. For example, a system 800 that incorporates a plug flow device 826 need not necessarily incorporate a first purge controller 820. Those skilled in the art who have reviewed the present disclosure will fully appreciate these and other changes that may be made to the system 800 without departing from the scope of the present invention.

  Electrochemical systems according to other embodiments of the invention may include additional components or exclude certain components described herein. For example, in a further embodiment illustrated in FIG. 9, the electrochemical system 900 includes a volume 918 and an accumulator 916 having a gas absorbing material or catalytic material 925, and a gas such as oxygen or hydrogen or both to the volume 918. Help to absorb or react. For example, the substance 925 can react with oxygen in the air that is drawn back to the accumulator 916 during shutdown and prevent oxygen from entering the anode or cathode.

  Further, the electrochemical system 900 may include a cathode recirculation line 923, similar to the anode recirculation line 623 discussed in connection with the illustrated embodiment of FIG. According to one embodiment, a recirculation device 922, such as an injection pump or blower, to recirculate the cathode gas through the recirculation line 923 and prevent gas or liquid from blocking the cathode channel 904. Can be used. In addition or alternatively, when the fuel cell stack 901 is disconnected, the oxidant is also recycled through the cathode recycle line 923 while oxygen is substantially consumed from the air in the fuel cell stack 901. Is possible. One skilled in the art will appreciate that the anode and cathode recirculation lines can be incorporated into any of the embodiments described herein.

  Furthermore, an electrochemical system 1000 according to yet another embodiment is illustrated in FIG. The electrochemical system 1000 may include a first purge control device 1020 disposed downstream of the storage device 1016 and a second purge control device 1052 disposed downstream of the anode channel 1002 and upstream of the storage device 1016. . The second purge controller 1052 can be closed or opened and / or adjusted therebetween to maintain or change the pressure of the fuel cell stack 1001, such as the pressure of the anode channel 1002. Further, the second purge control device 1052 is configured to control and / or stop fluid flow between the anode channel 1002 and the storage device 1016.

  In one embodiment, the method of operation of the electrochemical system 1000 includes maintaining the first and second purge controllers 1020, 1052 closed during normal operation of the fuel cell stack 1001. If it is desired to purge the fuel cell stack 1001, the first purge control device 1020 remains closed while the second purge control device 1052 is opened to pressurize the accumulator 1016. Then, while the first purge control device 1020 is opened, the second purge control device 1052 is closed and the storage device 1016 is opened. In some embodiments, a sensor 1054 disposed within or near the storage device 1016 can trigger a purge of the fuel cell stack 1001. For example, the sensor 1054 can monitor and / or measure the magnitude of the pressure in the storage device 1016 and trigger a purge upon detecting a threshold and / or a predetermined pressure magnitude.

  In addition or alternatively, the purge can be triggered based on a predetermined time interval, such as every minute, or every 30 seconds, or any other suitable time. In embodiments that incorporate a pressure-based and / or time-based method of purging, the first and second because a specific amount of fluid, such as a hydrogen-containing fuel, is purged from the fuel cell stack 1001 during each purge state. The purge control devices 1020, 1052 do not have to have a specific size or a specific dimension with accurate tolerances.

  In some embodiments, repetitive purging of the fuel cell stack 1001 can occur without opening the first purge controller 1020 when a fuel purge condition occurs. For example, during normal operation when the second purge control device 1052 is closed, a pressure differential is created between the anode channel 1002 and the storage device 1016. If a fuel purge is desired, the second purge control device 1052 can be opened and a fluid such as a hydrogen-containing fuel can be discharged into the storage device 1016. Thereafter, when the storage device purge condition occurs, for example, when the storage device 1016 is substantially filled with fluid and / or when the system 1000 is shut down, the first purge control device 1020 is opened to store the storage device. It is possible to purge the fluid accumulated from 1016 to the surrounding environment such as the atmosphere.

  In yet another embodiment, the hydrogen-containing fuel released from the storage device 1016 can be discharged into the cathode outlet to immediately reduce the concentration of hydrogen released into the atmosphere.

  In still other embodiments, purge control devices 1020 and 1052 are combined into a single three-way valve by a common port attached to accumulator 1016 and two other ports to 1023 and 1040 (not shown). Also good.

  One of ordinary skill in the art can incorporate a second purge control device similar to that discussed above in any of the embodiments described herein, the sensor 1054 can be a fuel cell stack and May be configured to detect other parameters, such as temperature and / or concentration of the fluid, instead of or in addition to the pressure of the fluid in the accumulator before inducing the purge of the accumulator Will fully understand.

  Additionally or alternatively, the second purge control device 1052 can be used in some embodiments as a pressure regulator. For example, during an up transient or load increase, the air pressure is typically increased. Therefore, it is desirable to increase the hydrogen pressure in a rapid manner to accommodate the increase in air pressure. Thus, closing the second purge controller 1052 increases the rate at which the anode pressure rises during periods when the upload transient continues to reduce the anode loop volume.

  Conversely, during downward transients or load reduction, the air pressure is reduced, minimizing parasitic power losses associated with the air compressor used to pressurize the air, which in turn results in less water production. obtain. In order to accommodate the decrease in air pressure, it is desirable to reduce the hydrogen pressure in a rapid manner to avoid unacceptably high transverse pressure in the fuel cell stack 1001. Thus, by opening the second purge control device 1052 during the period of falling load transients, when hydrogen-containing fuel is energized from the anode channel 1002 to the storage device 1016 due to the pressure difference therebetween, the anode channel 1002 Release the pressure inside. To further reduce the pressure, the first purge control device 1020 may open simultaneously with the second purge control device 1052 or alternatively switch between 1020 and 1052.

  In other embodiments, the sensor can be configured to detect oxidant pressure changes, and the second purge controller 1052 operates in a manner similar to that described above, resulting in the fuel cell stack 1001 as a result. It is possible to adjust the resulting pressure differential. In addition or alternatively, the pressure in the anode channel 1002 can be monitored as well, and once the threshold fuel or oxidant pressure and / or the desired transverse pressure between the anode and cathode layers is reached, the second The purge control device 1052 returns to its normal state depending on whether it is closed or open, and can deal with the abnormal state as described above.

  In any of the above embodiments, the pressure sensor (not shown) is a fuel cell stack 501, 601, 701, 801, 901 such as, for example, a cathode inlet, a cathode outlet, an anode inlet, and / or an anode outlet. , 1001 at the inlet and / or outlet. The pressure sensor can be used to monitor the pressure of the gas, and the information from the pressure sensor is used, for example, to control the air supply flow rate, the fuel supply flow rate, or the state of the first purge controller. be able to.

  In any of the above embodiments, in addition or alternatively, the storage devices 516, 616, 716, 816, 916, 1016 are fuel cell stacks 501, 601, 701, 801 instead of being isolated devices. , 901, 1001 may be included in the end hardware. Those skilled in the art who have reviewed the present disclosure will fully appreciate these and other changes that may be made to the system without departing from the spirit of the invention.

  A method for discontinuing operation of a fuel cell system, such as that shown in FIG. 5, will be described below in this application. First, the main load 542 is disconnected from the fuel cell stack 501. The fuel supply 510 is then terminated by closing the first flow control device 508 (also separating the fuel supply 510 from the stack 501). Oxygen in the air present in the cathode channel 504 is consumed as hydrogen diffuses through the ion exchange membrane 506 from the anode channel 502 to the cathode channel 504. Compared to the stoichiometric amount of oxygen in the air present in the cathode channel 504, the stoichiometric amount of hydrogen in the fuel present in the anode channel 502 and storage device 516 is the fuel cell system. More preferably, at least to some extent in the anode channel 502 after the oxygen is substantially consumed so that it is sufficient to actually consume substantially all of the oxygen in the cathode channel 504 at 500 outages. The total volume of anode channel 502, cathode channel 504, and storage device 516 should be sized appropriately so that there is excess hydrogen. When the fuel cell stack 501 is operated at an anode overpressure during normal operation (eg, the anode pressure is greater than the cathode pressure), the first purge controller 520 is depleted of hydrogen from the anode channel 502. When the anode pressure reaches or falls below the cathode pressure (eg, as determined by the anode and cathode pressure sensors upstream and / or downstream of the fuel cell stack 501), it can be opened.

  During operation, any excess fuel and / or other inert fluid that accumulates on the anode is stored in storage device 516. Thus, if hydrogen diffuses out of the anode channel 502 and reacts with residual oxygen in the cathode channel 504 during oxygen consumption during shutdown of the fuel cell system 500, excess fuel in the fuel outlet line 515 and / or storage device 516 is excessive. Fuel and / or other inert fluids are drawn back into the anode channel 502 and replace the diffused hydrogen. Since the first purge controller 520 is initially closed during oxygen consumption, the anode pressure decreases. When the anode pressure drops to and / or below the cathode pressure, air from the vent 540 and / or the air source 514 is drawn back into the storage device 516 and the excess that was present in the storage device 516 The first purge controller 520 is opened so that it can replace fuel and / or other inert fluids, thus preventing a near vacuum from being created in the anode channel 502.

  In addition, since oxygen is being consumed from cathode channel 504 during oxygen consumption, air can also be drawn into outlet line 517 and / or cathode channel 504 to replace the consumed oxygen. The process continues until oxygen is substantially consumed from the cathode channel 504. As a result, hydrogen, nitrogen, or a mixture thereof remains in the anode channel 502 after the shutdown is complete, thereby preventing air (and oxygen) from being introduced into the anode channel 502. After the oxygen is substantially consumed in the fuel cell stack 501, the shutdown of the fuel cell system 500 is completed.

  As described above in connection with the illustrated embodiment illustrated in FIG. 9, the storage device 916 is a substance 925 that reacts with oxygen when air is drawn back into the storage device 916 during hydrogen diffusion during shutdown. May further be included. Thus, oxygen in the air or cathode fluid that is drawn back into the storage device 916 and / or the cathode channel 904 undergoes a reaction to prevent oxygen from being present in the storage device 916 and further oxygen enters the anode channel 902. To prevent. Further, the size of the storage device 916 may be minimized.

  Further, the auxiliary load 544 illustrated in FIG. 5 can be connected to the fuel cell stack 501 to increase the rate of oxygen consumption of oxygen present in the cathode. The power can be used to supply power to either system components such as radiator fans or blowers or vehicle devices, or can be stored in an energy storage device such as a battery (not shown). . Those skilled in the art will recognize other system components that can be used to consume power and are not further illustrated.

  Another implementation of a fuel cell system containing oxygen and / or hydrogen sensors located at different points in a line leading to or extending from a storage device, such as a fuel cell system 800 as shown in FIG. In form, information from the oxygen and / or hydrogen sensors 828, 830 can be used to control the first purge controller 820. For example, the first purge controller 820 can be closed when the oxygen and / or hydrogen concentration reaches and / or exceeds a predetermined value during and / or after completion of the shutdown.

  In any of the embodiments described herein, the system 500, 600, 700, 800, 900, 1000 is the storage device 516 during and after the purge of the system 500, 600, 700, 800, 900, 1000. , 616, 716, 816, 916, 1016, combustor or dilution downstream of the first purge controller 520, 620, 720, 820, 920, 1020 configured to consume or dilute the fluid flow exiting the A vessel (not shown) may be included. In this way, any residual concentration of hydrogen is consumed, making this embodiment more suitable for applications that require strict emission standards.

  In addition, or alternatively, fluid exiting each storage device 516, 616, 716, 816, 916, 1016 may be stored in the storage device 516, 616, 716, 816, 916, 1016, and / or the first purge control device. 520, 620, 720, 820, 920, 1020 to the respective oxidant inlet downstream of the second flow controller 512, 612, 712, 812, 912, 1012 via a purge line downstream of Can do. In these embodiments, the purge line can be connected to a line upstream of the cathode channels 504, 604, 704, 804, 904, 1004. Such an arrangement also eliminates the need to use a combustor or diluter, and also prevents mass release of hydrogen from the accumulator to the atmosphere during the purge of the system 500, 600, 700, 800, 900, 1000.

  In any of the previous embodiments, the second flow control devices 512, 612, 712, 812, 912, 1012 may be opened or closed during shutdown.

  Of the above-mentioned U.S. patents, U.S. patent publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications referenced herein and / or listed in the application data sheet. All are hereby incorporated by reference in their entirety.

  From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications can be made without departing from the spirit and scope of the invention. Will be understood. Accordingly, the invention is not limited except as by the appended claims and their equivalents.

FIG. 1 is an exploded isometric view of a prior art membrane electrode assembly. FIG. 2 is an exploded isometric view of an electrochemical fuel cell according to the prior art. FIG. 3 is an isometric view of an electrochemical fuel cell stack according to the prior art. FIG. 4 is a block diagram of a conventional electrochemical system. FIG. 5 is a block diagram of an electrochemical system according to an embodiment of the present invention. FIG. 6 is a block diagram of an electrochemical system according to another embodiment of the present invention. FIG. 7A is a block diagram of an electrochemical system according to yet another embodiment of the present invention. FIG. 7B is a block diagram of an electrochemical system in a first state of operation, according to yet another embodiment of the present invention. FIG. 7C is a block diagram of the electrochemical system of FIG. 7B in a second state of operation. FIG. 8 is a block diagram of an electrochemical system according to another embodiment of the present invention. FIG. 9 is a block diagram of an electrochemical system according to yet another embodiment of the present invention. FIG. 10 is a block diagram of an electrochemical system according to yet another embodiment of the present invention.

Claims (29)

A plurality of fuel cells forming a fuel cell stack, each fuel cell comprising:
A membrane electrode assembly (MEA) having an ion exchange membrane inserted between the anode electrode layer and the cathode electrode layer;
An anode flow field plate adjacent to the first side of the MEA, the anode flow field plate configured to direct hydrogen-containing fuel to at least a portion of the first side of the MEA;
A cathode flow field plate adjacent to the second side of the MEA, the cathode flow field plate configured to induce oxidant in at least a portion of the second side of the MEA. A plurality of fuel cells,
At least one storage device disposed downstream of and in fluid communication with the fuel cell stack, the storage device operating to store and dispense fluid;
An oxidant outlet disposed downstream of the fuel cell stack;
A first purge control device disposed downstream of the storage device, wherein the first purge control device enables fluid communication between at least a portion of the anode flow field plate and at least a portion of the cathode flow field plate. And a first purge control device operable in a second state for separating the oxidant outlet from the storage device. A first flow control device disposed upstream of the fuel cell stack and configured to selectively control a flow rate of the hydrogen-containing fuel from a fuel supply source to the anode electrode layer of the fuel cell;
A second flow control device disposed upstream of the fuel cell stack and configured to selectively control a flow rate of the oxidant from an oxidant source to the cathode electrode layer of the fuel cell; The electrochemical system according to claim 1, comprising:   At least one sensor disposed proximate to the storage device and electrically connected to at least one of the first and second flow control devices, wherein the hydrogen downstream of the fuel cell stack And at least one indication of the hydrogen concentration and the oxygen concentration is electrically connected to at least one of the first and second flow control devices. The electrochemical system of claim 2, further comprising at least one sensor that communicates to control a flow rate of at least one of the hydrogen-containing fuel and the oxidant.   The at least one storage device includes a diaphragm that operates to maintain at least one of a transverse pressure of the fuel cell stack and a supply flow rate of at least one of the hydrogen-containing fuel and the oxidant; The electricity of claim 1, wherein the diaphragm includes a bias pressure device configured to increase the volume of the storage device in fluid communication with the anode electrode layer in response to a decrease in pressure of the cathode channel. Chemical system.   The electrochemical system of claim 1, wherein the at least one storage device further comprises a gas absorbing material.   The electrochemical system of claim 1, wherein the at least one storage device further comprises a material capable of at least one of oxidation and reduction when reacted with an oxidant.   The electricity of claim 1, further comprising at least one recirculation line upstream of the purge controller and operative to recirculate at least one of a portion of the fuel stream and a portion of the oxidant stream. Chemical system.   The electrochemical system of claim 7, further comprising an apparatus operable to facilitate the recirculation of a portion of the fuel stream and a portion of the oxidant stream.   The electrochemical system of claim 7, wherein the storage device includes at least one catalyst for reacting at least two gases.   The electrochemical system of claim 1, wherein the at least one storage device comprises at least one of a plug flow device and a biasing member comprising at least one of a spring and an actuator.   A second purge control device disposed downstream of the anode channel and upstream of the storage device, the second purge control device configured to control fluid flow between the anode channel and the storage device; The electrochemical system of claim 1, further comprising: A method for stopping operation of an electrochemical system having a plurality of fuel cells forming a fuel cell stack, each fuel cell having an ion exchange membrane inserted between the anode electrode layer and the cathode electrode layer A membrane electrode assembly (MEA) having and an anode flow field plate disposed adjacent to the anode electrode layer, configured to direct hydrogen-containing fuel from a fuel source to a portion of the anode electrode layer An anode flow field plate and a cathode flow field plate disposed adjacent to the cathode electrode layer, the cathode configured to induce oxidant from a source of oxidant to a portion of the cathode electrode layer A flow boundary plate and at least one storage device in fluid communication with at least a portion of at least one of the anode electrode layer and the cathode electrode layer;
Disconnecting the main load from the fuel cell stack;
Terminating the supply of fuel to the disconnected fuel cell stack;
After ending the supply of fuel, substantially consuming oxygen from the air in the cut fuel cell stack to form oxygen-deficient air therein;
Providing at least one of hydrogen and nitrogen to at least a portion of at least one of the anode electrode layers from the storage device.   The storage device is a plug flow device, and the method includes passively storing and dispensing at least one of hydrogen, oxygen and nitrogen into and from the plug flow device, respectively. The method of claim 12 further comprising:   13. The storage device of claim 12, wherein the storage device comprises a material that can be oxidized or reduced upon reaction with oxygen, and the method further comprises reacting the material with oxygen drawn to the storage device. Method. 13. The diaphragm of claim 12, wherein the storage device comprises a diaphragm including a bias pressure device configured to increase the volume of the storage device in fluid communication with the anode channel in response to a decrease in pressure of the cathode channel. A method as described,
The method further comprises maintaining a transverse pressure of the fuel cell stack as a function of the position of the bias pressure device by adjusting the volume of the storage device. The method of claim 12, wherein the electrochemical system further comprises at least one flow control device downstream of the fuel cell stack and in fluid communication with the fuel cell stack and the storage device.
Opening the at least one flow control device when the anode pressure is less than or equal to the cathode pressure of the fuel cell stack before or during substantially consuming oxygen in the air in the fuel cell stack; ,Method.   The method of claim 12, further comprising connecting an auxiliary load to the disconnected fuel cell stack to consume oxygen in the air therein. The electrochemical system further comprises a recirculation line upstream of the accumulator and operative to recycle at least one of a portion of the fuel stream and a portion of the oxidant stream. A method as described,
Recirculating at least one of the portion of the fuel stream and the portion of the oxidant stream.   Detecting the concentration of at least one of hydrogen and oxygen and communicating the indication of the at least one of the hydrogen concentration and the oxygen concentration to the at least one flow controller. 16. The method according to 16. Method of operating an electrochemical system having a plurality of fuel cells forming a fuel cell stack, each fuel cell having an ion exchange membrane inserted between an anode electrode layer and a cathode electrode layer (MEA), an anode flow field plate disposed adjacent to the anode electrode layer and configured to direct hydrogen-containing fuel to the anode electrode layer, and disposed adjacent to the cathode electrode layer, the cathode A cathode flow field plate configured to direct oxidant to the electrode layer; at least one storage device disposed downstream of the fuel cell stack; a cathode inlet disposed upstream of the fuel cell stack; An oxidant outlet disposed downstream of the fuel cell stack and a downstream of the storage device to allow fluid communication between the anode flow field plate and the cathode flow field plate. And a first purge control device operable in a second state separating the oxidant outlet from the storage device and between the fuel cell stack and the storage device, the anode flow field A second state operable in a first state allowing fluid communication between the plate and the storage device and a second state discontinuing fluid communication between the anode flow field plate and the storage device. A purge control device, the method comprising:
Upon detecting a fuel cell stack purge condition, opening the second purge controller for a first time to operate in the first condition and purge fluid from the anode flow field plate to the storage device When,
Closing the second purge control device to operate in the second state;
When the storage device purge state is detected, the first purge control device is opened for the second time after the first time to supply fluid from the storage device to at least one of the ambient environment and the cathode inlet. Performing a storage device purge by purging. Detecting a magnitude of at least one operating parameter of the fuel cell stack;
Comparing the magnitude of the at least one operating parameter of the fuel cell stack with a magnitude of the first threshold to determine the presence of the fuel cell stack purge condition;
Initiating a fuel cell stack purge when the magnitude of the at least one operating parameter of the fuel cell stack is substantially the same as or greater than the magnitude of the first threshold. Item 21. The method according to Item 20.   21. The method of claim 20, wherein the at least one operating parameter comprises at least one of a concentration, pressure and temperature of at least one of hydrogen, oxygen and nitrogen.   The at least one operating parameter includes an anode flow boundary plate, an anode recirculation line, an anode fuel inlet disposed between a fuel source and the fuel cell stack, and between the fuel cell stack and the storage device. The method of claim 21, wherein the method is detected proximate to at least one of the disposed anode fuel outlets. Detecting a magnitude of at least one operating parameter of the storage device proximate to at least one of the storage device, the first purge control device, and the second purge control device;
Comparing the magnitude of the at least one operating parameter of the accumulator with a magnitude of a second threshold to determine the presence of the accumulator purge condition;
The method further comprises initiating an accumulator purge when the magnitude of the at least one operating parameter of the accumulator is approximately the same as or greater than the magnitude of the second threshold. The method described in 1.   25. The method of claim 24, wherein the at least one operating parameter includes at least one of a concentration, pressure, and temperature of at least one of hydrogen, oxygen, and nitrogen. Detecting the passage of the first threshold time, starting the fuel stack purge;
21. The method of claim 20, further comprising the step of initiating the accumulator purge upon detecting passage of a second threshold time.   21. The method of claim 20, further comprising extracting a main load from the fuel cell stack. Method of operating an electrochemical system having a plurality of fuel cells forming a fuel cell stack, each fuel cell having an ion exchange membrane inserted between an anode electrode layer and a cathode electrode layer (MEA), an anode flow field plate disposed adjacent to the anode electrode layer and configured to direct hydrogen-containing fuel to the anode electrode layer, and disposed adjacent to the cathode electrode layer, the cathode A cathode flow field plate configured to direct oxidant to the electrode layer; at least one storage device disposed downstream of the fuel cell stack; and disposed between the fuel cell stack and the storage device; In a first state allowing fluid communication between the anode flow field plate and the storage device and in a second state discontinuing fluid communication between the anode flow field plate and the storage device And a purge control unit is possible work, the method comprising,
Detecting an increase in load applied to the fuel cell stack and an increase in at least one of the pressure and concentration of the oxidant in the fuel cell stack;
Operating in the second state to increase at least one of the pressure and concentration of the hydrogen-containing fuel in the fuel cell stack and to balance the pressure difference of the fuel cell stack Closing the controller. Method of operating an electrochemical system having a plurality of fuel cells forming a fuel cell stack, each fuel cell having an ion exchange membrane inserted between an anode electrode layer and a cathode electrode layer (MEA), an anode flow field plate disposed adjacent to the anode electrode layer and configured to direct hydrogen-containing fuel to the anode electrode layer, and disposed adjacent to the cathode electrode layer, the cathode A cathode flow field plate configured to direct oxidant to the electrode layer; at least one storage device disposed downstream of the fuel cell stack; and disposed between the fuel cell stack and the storage device; In a first state allowing fluid communication between the anode flow field plate and the storage device and in a second state discontinuing fluid communication between the anode flow field plate and the storage device And a purge control unit is possible work, the method comprising,
Detecting an increase in load applied to the fuel cell stack and a decrease in at least one magnitude of the pressure and concentration of the oxidant in the fuel cell stack;
Operating in the first state to reduce at least one of the pressure and concentration of the hydrogen-containing fuel into the fuel cell stack and balance the pressure difference of the fuel cell stack Opening the purge control device.

Images